The present invention relates to an air pressure warning device of a vehicle tire and, more particularly, to an air pressure warning device which can prompt a user to appropriately adjust the tire air pressure during or before traveling on an expressway.
Conventionally, a technique for detecting the air pressure of a vehicle tire, and informing the user of the detected (measured) air pressure as a tire air pressure state is known.
As such technique, for example, Japanese Patent Laid-Open No. 2001-33259 discloses that when a tire pressure drop is detected in a vehicle, information indicating the tire pressure drop and a travel route to a gas station are displayed on the screen of a navigation device.
According to this prior art, when the tire air pressure has dropped, since the travel route to a gas station where the air pressure can be adjusted is displayed on the navigation screen, a driver (passenger) can quickly adjust the air pressure.
When a vehicle runs on an expressway, it is preferable for safety to increase the tire air pressure of that vehicle by a predetermined value compared to a case wherein the vehicle runs on open roads.
However, even when the user has such knowledge, he or she does not always practice it every time the vehicle runs on an expressway, i.e., the tire air pressure is not always appropriately adjusted every time the vehicle runs on an expressway.
The present invention has been proposed to solve the conventional problems, and has as its object to provide an air pressure warning device of a vehicle tire, which positively displays an excessive/deficient state of the tire air pressure during or before traveling on an expressway so as to arouse user""s awareness of tire air pressure adjustment and to promote appropriate tire air pressure adjustment.
In order to achieve the above object, the present invention adopts the following solution.
That is, in order to achieve the above object, the first arrangement of the present invention is an air pressure warning device (10) of a vehicle tire, which comprises tire air pressure detection means (6-9), attached to a vehicle tire, for detecting a tire air pressure, and informing means (11) for informing a tire air pressure state on the basis of the tire air pressure detected by the tire air pressure detection means, characterized by comprising:
storage means (10a) for storing a normal air pressure of the tire;
calculation means (10b) for calculating an excessive/deficient amount of a measured air pressure of the tire from the normal air pressure on the basis of a relationship between the normal air pressure stored in the storage means and the air pressure detected by the tire air pressure detection means;
expressway traveling detection means (10d) for detecting if the vehicle is traveling on an expressway or if the vehicle will travel on the expressway before the beginning of actual traveling; and
informing control means for controlling the informing means to inform the excessive/deficient amount calculated by the calculation means as an air pressure state of the tire, and
in that the informing control means (10c) controls the informing means to inform a deficient amount larger than an actual amount upon informing the deficient amount of the measured air pressure of the tire from the normal air pressure, by correcting to increase the normal air pressure read out from the storage means by a predetermined value, and setting the corrected normal air pressure in the calculation means, when the expressway traveling detection means detects that the vehicle is traveling on the expressway, or detects possibility of traveling on the expressway before the beginning of actual traveling.
According to the first arrangement of the present invention, since the normal air pressure is set to be higher by the predetermined value during or before traveling on the expressway of the vehicle, even when the tire air pressure is not deficient with respect to the normal air pressure under ordinary circumstances, the calculation means calculates a deficient amount in the state wherein the normal air pressure has been corrected to a relatively higher value, and the informing means informs that deficient state.
When the user recognizes information of the deficient state, he or she becomes aware of the need for pumping air in a tire. For example, the user replenishes air in a tire at a gas station in a service area during traveling on the expressway, or at a gas station along an open road before heading toward an expressway ramp.
That is, according to the present invention, since the deficient state of the tire air pressure is positively displayed during or before traveling on the expressway, user""s awareness of air pressure adjustment can be aroused, thus promoting appropriate tire air pressure adjustment.
In the second arrangement of the present invention, the expressway traveling detection means (10d) detects, on the basis of a communication for expressway toll collection between a communication unit (12) mounted on the vehicle and a unit (13) equipped on the road side, if the vehicle is traveling on the expressway.
According to the second arrangement of the present invention, the state before the beginning of traveling on the expressway can be recognized using an onboard unit used in a so-called electronic toll collection system.
In the third arrangement of the present invention, the expressway traveling detection means (10d) comprises navigation means (14) which includes current position detection means (14a) for detecting a current position of the vehicle, and travel route setting means (14b) for setting a travel route of the vehicle to a destination, and the expressway traveling detection means detects that the vehicle is traveling on the expressway or predicts that the vehicle will travel on the expressway, when the current position of the vehicle detected by the current position detection means indicates that the vehicle is present on the expressway, or when the travel route set by the travel route setting means includes the expressway.
According to the third arrangement of the present invention, the expressway traveling state or the state before the beginning of traveling on the expressway can be recognized using navigation means.
In the fourth arrangement of the present invention, the navigation means (14) includes display means (14d) for displaying the current position of the vehicle detected by the current position detection means (14a) and the travel route to the destination set by the travel route setting means (14b) together with a map image, and when the calculation means calculates the excessive/deficient amount of the tire air pressure, the informing control means controls the navigation means to display information associated with a facility where the tire air pressure can be adjusted on a travel route from the current position of the vehicle to an approach ramp of the expressway.
According to the fourth arrangement of the present invention, when the excessive/deficient state of the tire air pressure is detected, since the facility that allows to adjust the tire air pressure is displayed on the travel route from the current position of the vehicle to an approach ramp to the expressway, the driver can easily acquire information associated with the facility that allows to adjust the tire air pressure before the beginning of traveling on the expressway.
In the fifth arrangement of the present invention, when the display means displays the information associated with the facility where the tire air pressure can be adjusted, the navigation means (14) can guide the travel route to the destination by way of that facility.
According to the fifth arrangement of the present invention, since the travel route is guided by way of the facility that allows to adjust the tire air pressure, the driver can easily reach the facility that allows to adjust the tire air pressure.
In the sixth arrangement of the present invention, when the calculation means calculates the excessive/deficient amount of the tire air pressure, the navigation means (14) can guide a travel route that excludes the expressway detected by the expressway travelling detection means as the travel route from the current position of the vehicle to the destination.
According to the sixth arrangement of the present invention, when the excessive/deficient state of the tire air pressure is detected, since a travel route that detours around the expressway is guided, the travel route to the destination without using the expressway can be presented to the user, e.g., when there is no facility that allows to adjust the tire air pressure from the current vehicle position to an approach ramp of the expressway.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.